The e-h plasma at 2 K in direct-gap GaAs1-xPx is studied for x=0.38. At high pumping levels an expansion of the plasma, directly observable through its luminescent emission, sets in when the excited particle density reaches the liquid density nāā5Ć1016 pairs cm-3. The spectral lineshape of the luminescence collected from the whole plasma region differs appreciably from that obtained restricting the observation to the pumped region alone. Plasma expansion and spectral emission are accounted for by a hydrodynamic model, where the particle flow due to Fermi pressure is fast enough to overcome recombination.
